Method and apparatus for killing weeds



Dec. 30, 19.69

R. c. PIVONKA METHOD AND APPARATUS FOR KILLING WEEDS 2 Sheets-Sheet 1Filed Oct. 10, 1967 INVENTOR. RALPH C. P/I O/VKA Dec. 30, 1969 R.PlVONKA 3,486,497

METHOD AND APPARATUS FOR KILLING WEEDS Filed Oct. 10, 196'? 2Sheets-Sheet 2 Pig. 2

INVENTOR.

RALPH C. P/VO/V/(A United States Patent 3,486,497 METHOD AND APPARATUSFOR KILLING WEEDS Ralph C. Pivonka, La Crosse, Kaus., assignor to WarrenPetroleum Corporation, Tulsa, Okla., a corporation of Delaware FiledOct. 10, 1967, Ser. No. 674,292

Int. Cl. F23c 5/00; F23d 11/44 US. Cl. 126271.2 6 Claims ABSTRACT OF THEDISCLOSURE This invention relates to the killing of weeds and moreparticularly to a method and apparatus for killing weeds with a flame.

It is frequently desirable to kill the weeds along the shoulders of aroad, in irrigation or drainage ditches, or around equipment located inan open field. Sometimes it is desirable to ignite brush over a largearea to start a back fire to prevent spread of forest fires. One methodthat has been used to kill weeds is by directing a flame or hotcombustion gases against weeds. Because of the very large areas of roadshoulders, irrigation ditches, etc., a burner capable of releasing heatat high rates over a large area is desired.

The burners heretofore available either for flame cultivation ornonselective killing of weeds have had a limited heat release capacityGenerally, the ignition of the fuel occurs within a torch from whichflame and hot combustion gases are discharged and directed against theweeds to be killed. The large volume of hot gases that pass through theburner necessitate a burner of large size even for very low heat releasecapacities. Moreover, the blast of hot gases discharged from the burnersfrequently cannot penetrate deeply into brush or through thick growthsof weeds because of the shielding of the foliage. Much of the heatreleased by the combustion is wasted by being diverted from cont-actwith the weeds.

This invention resides in a method and apparatus for the nonselectivekilling of weeds in which a fine stream of liquid fuel is discharged ata high velocity through an orifice onto the area to be cleared andsimultaneously moving a flame directed onto that area to ignite the fuelsubstantially at the location of impact of the fuel stream with theground or other solid surface. In the apparatus, an orifice of smalldiameter serves as an outlet for a liquid fuel line to discharge thefine stream of fuel, and a vaporizing torch is positioned to discharge aflame in the same direction as the liquid stream.

In the drawings:

FIGURE 1 is a longitudinal sectional view of the weed burner of thisinvention;

3,486,497 Patented Dec. 30, 1969 ice FIGURE 2 is a front elevationalview of the weed burner mounted on a tractor; and

FIGURE 3 is a horizontal sectional view through one type of orifice capto be used for controlling the spray pattern of liquid fuel used to burnthe weeds.

Referring to FIGURE 1 of the drawings, the weed burner indicatedgenerally by reference numeral 10 has an LPG supply line 12 forconnection to a fuel storage tank of suitable size depending uponthe'use of the particular burner. Any fuel which is suflicientlyvolatile at atmospheric temperatures to rapidly form a combustiblemixture of fuel and air that can be ignited by momentary contact with aflame can be used. A preferred fuel is LPG. LPG has a high enough vaporpressure to provide the pressure required to operate the liquid sprayand torch without auxiliary equipment. 'It also vaporizes quickly toform a combustible gaseous mixture that is immediately ignited oncontact with a flame. The term LPG as herein used includes propane,butane, mixtures of propane and butane, and mixtures of propane, butaneand higher boiling hydrocarbons such as pentane and hexane. Higherboiling hydrocarbons such as gasoline and kerosene can be used, butthose fuels require some means for raising the pressure high enough tooperate the liquid spray and torch. The necessary pressure can beobtained by mixing a volatile fuel such as propane with kerosene.Mixtures of kerosene or furnace oil with propane are advantageous incausing a longer burning flame with increased heat release as comparedWith propane alone. Fuels less volatile than kerosene are diflicult toignite and are not suitable unless mixed with propane or a similar fuel.For convenience, the fuel is hereinafter referred to as LPG in thedescription of this invention.

LPG supply line 12 is connected to a T 14 from which a liquid dischargeline 16 extends laterally and then changes in direction in an L 18. Theend of discharge line 16 is closed by an orifice cap 20 having anorifice 21 therein for spraying liquid LPG directly onto the ground. Anydesired arrangement of orifice in the orifice cap can be employed togive the desired spray pattern. In the orifice cap illustrated in FIGURE3 of the drawings, three orifices are provided to distribute streams ofliquid LPG over a relatively wide area. The orifices are designed todischarge a high velocity stream of small diameter. A single orifice 7inch in diameter has been found to give a long penetrating flame whenLPG is the fuel. Three orifices inch in diameter, such 'as illustratedin FIGURE 3, will give a fan-shaped flame.

A control valve 22 in line 16 permits adjustment of the rate ofdischarge of LPG from the weed burner. In the embodiment illustrated inFIGURE 1, a solenoid-operated valve 24 is provided to allow on-oifremote control of the flow. In a portable unit, a solenoid valve, suchas valve 24, will not be necessary and may be replaced with alever-operated, quick-closing valve if quick closing means are desired.

A torch supply line 26 provided with a control valve 28 andsolenoid-operated valve 30 extends from T 14 in a direction parallel tothe major part of discharge line 16 to a torch indicated generally byreference numeral 32. a

Supply line 26 is connected through a bushing 34 to a vaporizer tube 36.Vaporizer tube 36 is enclosed within a thimble 38 held in place aroundthe vaporizer tube 36 by a coupling 40 screwed on the outer surface ofbushing 34. A helical coil 42 in the annular space between the tube 36and thimble 38 increases the distance the gases must travel and therebyimproves transfer of heat to the fluids in the torch.

Secured to the outer surface of the thimble 38 are a pair of nozzleassemblies 44 which have restricted outlets 46 for discharging vaporizedLPG at a high velocity. Holes are drilled in the wall of the nozzleassemblies 44 and tube 36 to provide passages 45 through which LPG flowsinto the nozzle assemblies 44. A sleeve 47 surrounds the nozzleassemblies 44 and is spaced therefrom to allow flow of air through thesleeve toward its outlet end 49. The outlet end of the sleeve isapproximately in line with the orifice cap 20 while the tube 36 andthimble 38 extend beyond the orifice cap. The torch 32 is described andclaimed in my application Ser. No. 482,082, field on Aug. 24, 1965, nowPatent No. 3,357,474 and entitled Combined Fuel Vaporizer and Torch.

In the operation of the weed killer, the valve 28 and valve 30 areopened to allow LPG to flow through the torch supply line 26 and tube 36into thimble 38. The LPG then flows back through the annulus betweentube 36 and thimble 38, into nozzle assemblies 44, and out throughorifices 46. The LPG discharged from orifice 46 is then ignited by anysuitable means. The flame resulting from ignition of LPG heats thimble38 which transfers heat to the LPG flowing therethrough and vapor zesthat LPG, whereupon the LPG is discharged through nozzles 46 at a highvelocity. Air is drawn into the upper open end of sleeve 32 for mixturewith LPG within the sleeve. Valve 28 is adjusted to provide a flame ofthe desired length.

Valves 22 and 24 are opened to allow liquid LPG to flow through liquiddischarge line 16 and orifice 21 to discharge a stream of liquiddirectly onto the area or growth to be flamed. Upon vaporization at theground level or deep within brush and mixing with air to form acombustible mixture, the LPG is ignited by the flame from the torch 32.Moving the torch and stream of LPG simultaneously over the area to beflamed insures quick and complete ignition before vapors of fuel moveaway from the target area. A bracket 43 holds tube 16 and burner 32 infixed relation to one another to insure synchronization of theirmovement.

A combustible mixture of air and LPG is formed onl after vaporization ofthe LPG after striking the target area. Combustion then occurs at thebase of the plants where the largest amount of heat is required forkilling weeds. The tendency of propane or butane to seek low levels whenvaporized, and especially when cooled by natural vaporization, aids theflames in adhering to the ground long periods. In this manner, the weedburning device of this invention allows eflicicnt utilization of theheat of combustion with resultant fuel savings of the order of 50percent or even more. Loss of heat to the atmosphere at some distancefrom the weeds is minimized.

For burning of weeds along roadways or irrigation ditches, one or moreweed burners are mounted on a tractor such as illustrated in FIGURE 2 ofthe drawings. Referring to FIGURE 2, a tractor indicated generally byreference numeral 50 is shown with a front-mounted platform 52 on whicha tank of LPG 54 is mounted. The tractor 50 is provided with a boom 56which may be raised and lowered by the hydraulic system of the tractor.Mounted on the outer end of the boom 56 is a burner 10. It will beappreciated that any number of desired burners may be mounted on theboom, and they can be inclined at any desired angle to discharge LPG toprovide the desired pattern of burning. The individual burners can bemade up with two or more nozzles for discharging liquid in combinationwith a single torch.

In the operation of the apparatus illustrated in FIG- URE 2, thesolenoid valve 30 is opened by a suitable switch within reach of thedriver. Valve 28 is opened and torch 32 lit. Valve 22 is opened to givethe approximate desired flow of LPG and then the solenoid valve 24 isopened from a position near the drivers seat. The tractor is then drivenalong the area to be treated. Because of the large amount of heat ofcombustion available in the liquid fuel, it is possible to drive thetractor at rates as high as fifteen miles per hour and effectively killweeds along the side of the road.

The weed burner of this invention allows the liberation of largequantities of heat from a compact apparatus. Delivery of the fuel as aliquid directly onto the ground causes the volume of the LPG in theburner to be small. By discharging a liquid stream of the LPG, the fuelcan be made to penetrate deeply through brush or other foliage beforeignition and thereby result in liberation of heat at locations which areonly difiiculty accessible in conventional burners.

I claim:

1. Apparatus for clearing weeds from an area comprising a fuel feed lineconnected at its inlet end to a liquid fuel supply line, a heat exchangesection in said fuel feed line between the inlet end and discharge endthereof, a burner nozzle connected to the discharge end of the fuel feedline positioned to direct burning fuel discharged therefrom away fromthe liquid fuel supply line and into contact with the heat exchangesection, a sleeve surrounding and spaced from the fuel feed line andburner nozzle and extending from the burner nozzle in the direction ofdischarge of fuel therefrom, a liquid fuel discharge line connected atits inlet to the fuel supply line, an orifice plate at the discharge endof the liquid fuel discharge line having an opening therein adapted todischarge a thin stream of liquid fuel, said liquid fuel discharge lineextending outside of, but adjacent to, the sleeve, and a valve in theliquid fuel discharge line for control of the flow of liquid fueltherethrough.

2. Apparatus as set forth in claim 1 in which the discharge end of thesleeve and of the liquid fuel discharge line are in substantially thesame plane.

3. Apparatus for clearing Weeds from an area comprising a fuel feed lineconnected at its inlet end to a fuel supply line, a burner nozzleconnected to the discharge end of the fuel feed line, a sleevesurrounding and spaced from the fuel feed line and burner nozzle andextending from the burner nozzle in the direction of discharge of fueltherefrom, a liquid fuel discharge line connected at its inlet end tothe fuel supply line and having its discharge end at a substantiallylarger distance than the burner nozzle from the liquid fuel supply line,an orifice plate at the discharge end of the liquid fuel discharge linehaving an opening therein adapted to discharge a thin stream of liquidfuel, said liquid fuel discharge line extending outside of the sleeve,and a valve in the liquid fuel discharge line for control of the flow ofliquid fuel therethrough.

4. Apparatus as set forth in claim 3 in which the liquid fuel storagetank is mounted on a tractor, a boom extends laterally from the tractor,and the liquid fuel discharge line and torch are mounted on the boomadjacent its outer end.

5. Apparatus as set forth in claim 4 including valves in the liquid fueldischarge line and liquid fuel feed line, and means operable from thedrivers seat of the tractor for operating the valves.

6. Apparatus for clearing weeds from an area comprising a liquid fueldischarge line connected to a fuel supply line, an orifice plate at thedischarge end of the liquid fuel discharge line having an openingtherein adapted to discharge a thin stream of liquid fuel, a valve inthe liquid fuel discharge line for control of flow therethrough, a fuelfeed line connected at its inlet end to the fuel supply line, a thimbleenclosing and spaced from the end of the fuel feed line remote from thefuel supply line a nozzle assembly mounted on the thimble 5 6 adjacentthe end of the thimble nearest the fuel supply 2,485,391 10/1949Lasseigne et a1. line, a passage through the wall of the thimble intothe 2,497,939 2/1950 Garraway et a1. 43191 X nozzle assembly, saidnozzle assembly having an outlet of 2,833,272 5/1958 Kennepohl 126271.2small diameter positioned to discharge fuel to the end of l the thimbleremote from the fuel supply line, and a valve FOREIGN PITTENTS in thefuelfeed line, 5 108,620 10/1939 Australia.

References Cited CHARLES I. MYHRE, Primary Examiner UNITED STATESPATENTS Cl. 1,008,733 11/1911 Roy et a1 43-144 10 431 243 1,820,3838/1931 Elze 431236

